Searching for Hidden Particles & getting rid of muons Oliver Lantwin [ oliver.lantwin@cern.ch ] ic student seminar 3rd November 2016
Hidden Particles Searching for Hidden Particles The catch: µs Conclusion Oliver Lantwin (Imperial College London) ic student seminar 2/22
Hidden Particles Searching for Hidden Particles The catch: µ s Conclusion Oliver Lantwin (Imperial College London) ic student seminar Hidden Particles 2/22
State of the Standard Model ◮ Know there is new physics: ◮ Dark Matter ◮ Baryogenesis ◮ Neutrino masses ◮ Don’t know where: no indications yet for scale between ew and Planck ◮ We’d better look everywhere we can ◮ Strongly interacting: lhc , fcc ? ◮ Super-weakly interacting: comet , lz , SHiP Oliver Lantwin (Imperial College London) ic student seminar Hidden Particles 3/22
Dark Sector models L = L sm + L portal + L ds Very general phenomenology: ◮ Something we know ( sm ), ◮ Something we think is there but don’t know ( ds /new physics), ◮ Hopefully a portal other than gravity eg. dark matter mediator Oliver Lantwin (Imperial College London) ic student seminar Hidden Particles 4/22
Many different portal models ◮ Scalar (e.g Higgs singlets) ◮ Fermions (e.g. heavy neutral leptons ( hnl )) ◮ Vectors (e.g. dark photons) Oliver Lantwin (Imperial College London) ic student seminar Hidden Particles 5/22
Hidden Particles Searching for Hidden Particles The catch: µ s Conclusion Oliver Lantwin (Imperial College London) ic student seminar Searching for Hidden Particles 5/22
Searching for Hidden Particles Clearly, if hidden particles: (A) can be created by colliding sm particles Oliver Lantwin (Imperial College London) ic student seminar Searching for Hidden Particles 6/22
Searching for Hidden Particles Clearly, if hidden particles: (A) can be created by colliding sm particles ↔ (B) can decay back to sm ◮ So if we assume (A) we can look for visible decays back to the sm (B) ◮ If we assume ¬ (A) hidden particles impossible to detect But doesn’t have to be annihilation/pair-production Oliver Lantwin (Imperial College London) ic student seminar Searching for Hidden Particles 7/22
Searching for Hidden Particles Clearly, if hidden particles: (A) can be created by colliding sm particles ↔ (B) can decay back to sm ◮ So if we assume (A) we can look for visible decays back to the sm (B) ◮ If we assume ¬ (A) hidden particles impossible to detect But doesn’t have to be annihilation/pair-production Oliver Lantwin (Imperial College London) ic student seminar Searching for Hidden Particles 7/22
Requirements Problem: Guess what also decays visibly: sm particles ◮ need to reject sm processes Portal processes need to be extremely rare, otherwise they would have been seen at general purpose experiments ◮ need extremely high intensity, no backgrounds Oliver Lantwin (Imperial College London) ic student seminar Searching for Hidden Particles 8/22
Requirements Problem: Guess what also decays visibly: sm particles ◮ need to reject sm processes Portal processes need to be extremely rare, otherwise they would have been seen at general purpose experiments ◮ need extremely high intensity, no backgrounds Oliver Lantwin (Imperial College London) ic student seminar Searching for Hidden Particles 8/22
Experimental sketch High intensity: ⇒ fixed target, dense target No background: ⇒ need to filter out sm before they’re detected, doing it during data analysis impossible ◮ Focus on visible decays allows higher intensity and use of proton beam: We don’t need to know the initial state! Oliver Lantwin (Imperial College London) ic student seminar Searching for Hidden Particles 9/22
Most of SHiP (ca. tp ) Evacuate vessel to get rid of neutrino interactions, add a hadron absorber... 2 × 10 20 protons on target at 400 GeV Oliver Lantwin (Imperial College London) ic student seminar Searching for Hidden Particles 10/22
What can we do with SHiP? See-saw hnl : Oliver Lantwin (Imperial College London) ic student seminar Searching for Hidden Particles 11/22
What can we do with SHiP? Dark Photons: Oliver Lantwin (Imperial College London) ic student seminar Searching for Hidden Particles 12/22
� � �� � What can we do with SHiP? Light DM scattering: Dark Matter (DM): prospects @ SHiP M A’ /M χ =5 ¡ 10 - 8 10 - 9 Y = � 2 � ' ( m � / m V ) 4 Courtesy ¡of ¡Patrick ¡ 10 - 10 deNiverville ¡ 10 - 11 SHiP 50 Events BaBar K + �� + + invisible Relic Density LSND Direct Detection E137 10 - 12 10 - 2 10 - 1 1 m � ( GeV ) SHiP would be able to probe even beyond relic density in minimal hidden-photon model Background from neutrino interactions must be under control Requires dedicated study! Beyond ¡Collider ¡Physics, ¡CERN ¡ 8 ¡ And a lot more! Oliver Lantwin (Imperial College London) ic student seminar Searching for Hidden Particles 13/22
SHiP (ca. tp ) But wait! We forgot the Muon sweeping magnets! Oliver Lantwin (Imperial College London) ic student seminar Searching for Hidden Particles 14/22
Hidden Particles Searching for Hidden Particles The catch: µ s Conclusion Oliver Lantwin (Imperial College London) ic student seminar The catch: µ s 14/22
The standard solution to muon background: Put your experiment under a mountain against cosmic µs Oliver Lantwin (Imperial College London) ic student seminar The catch: µ s 15/22
The problem with that: There is no mountain big enough for 10 11 per spill, but if there were, there wouldn’t be any signal left anyway... 1 . 6 GeV, 100000 events × 10 − 4 2 . 0 Beauty+Cascade Charm+Cascade 1 . 8 1 . 6 1 . 4 A ( N 2 , 3 → µπ ) 1 . 2 1 . 0 0 . 8 0 . 6 0 . 4 0 20 40 60 80 100 120 140 Distance of vessel from target (m) Oliver Lantwin (Imperial College London) ic student seminar The catch: µ s 16/22
Divert power to deflector shields Now, something like this would be better: How do you deflect charged particles? Magnets! Oliver Lantwin (Imperial College London) ic student seminar The catch: µ s 17/22
Muon shield 101 One magnet won’t do, but two basically works: Oliver Lantwin (Imperial College London) ic student seminar The catch: µ s 18/22
More realistic muon shield Y Side view Z Top view X Z But still room for improvement... Oliver Lantwin (Imperial College London) ic student seminar The catch: µ s 19/22
Because it determines what space is available for physics! Normalised µ occupancy for 5198390 µ Normalised µ occupancy for 5198390 µ 10 − 1 Envelope < 1 E − 06 muons 12 10 0 14 10 − 2 12 10 10 − 1 10 10 − 3 8 10 − 2 | x | [m] 8 | y | [m] 6 10 − 4 10 − 3 6 4 10 − 5 10 − 4 4 2 10 − 6 2 10 − 5 0 20 40 60 80 20 40 60 80 Distance from target z [m] Distance from target z [m] N → µµν acceptance envelope 6 x, 95% x, 99% x, 99 . 9% 5 x, 100% y, 95% y, 99% 4 y, 99 . 9% y, 100% | x | , | y | [m] 3 2 1 0 0 10 20 30 40 50 60 70 80 Distance from target z [m] Oliver Lantwin (Imperial College London) ic student seminar The catch: µ s 20/22
Because we can gain signal and save money with an optimised magnet Before ⇒ after 1 . 6 GeV, 100000 events 1 . 6 GeV, 100000 events × 10 − 4 × 10 − 4 2 . 0 2 . 0 Beauty+Cascade Beauty+Cascade Charm+Cascade Charm+Cascade 1 . 8 1 . 8 1 . 6 1 . 6 1 . 4 1 . 4 A ( N 2 , 3 → µπ ) A ( N 2 , 3 → µπ ) 1 . 2 1 . 2 1 . 0 1 . 0 0 . 8 0 . 8 0 . 6 0 . 6 0 . 4 0 . 4 0 20 40 60 80 100 120 140 0 20 40 60 80 100 120 140 Distance of vessel from target (m) Distance of vessel from target (m) +30% while saving 2500 t ≈ 7 . 5 M chf Oliver Lantwin (Imperial College London) ic student seminar The catch: µ s 21/22
Hidden Particles Searching for Hidden Particles The catch: µ s Conclusion Oliver Lantwin (Imperial College London) ic student seminar Conclusion 21/22
Conclusion ◮ Searching for hidden particles is a way to study a very general phenomenology with some very interesting models (including ν msm , ldm , R-parity violating susy ) ◮ But it’s hard: need dedicated experiments ◮ SHiP is currently in the design phase ◮ tdr -but-don’t-call-it-that-for-political-reasons in 2018/19 ◮ will start running 2026 ◮ This talk didn’t cover much of what I actually do... @ First years: join us! Oliver Lantwin (Imperial College London) ic student seminar Conclusion 22/22
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